I have been trying some of the immutable linux OSes because from what I understand they are more modern and feature better security and reliability. What I have found so far is shocking. Half of these don’t support my laptop (probably because it’s nvidia optimus). Some I tried like guix were very difficult to install, configure, and use with sprase documentation. Good luck trying to use KDE, wayland, or pipewire for example. BlendOS was notably better and could at least run on my laptop but chocked with nvidia driver issues.
I have switched to pop os on my laptop for now but looking at alternatives and what to install on my desktop.
I’m not sure how good a suggestion this is for you and your optimus usecase, but have you checked out the uBlue spins of Fedora Silverblue/Kinoite/etc? They pre-include stuff that Fedora won’t ship, like non-free codecs and nvidia drivers.
I’m prepping a swap from Arch Linux to my own Silverblue image based on their DIY guide at the moment, mainly to see how the whole immutable aspect feels day-to-day. The image-based updates in the background are just a bonus.